Are tension headaches caused by muscle tension?

They do not appear to be. For many years, though, researchers believed that tension headaches were caused by the contraction of neck and scalp muscles. Recent research has cast doubt on this theory. Electromyogram studies have not been unable to identify increased muscle tension in people diagnosed with tension headache. An electromyogram is a test used to record electrical currents produced by muscle activity. This shows that muscle tension may not be the main cause of tension headaches. Because of these findings, the International Headache Society has begun to refer to tension headaches as tension-type headaches.

If tension doesn't cause tension headaches, what does?

A new theory suggests that tension headaches are the result of changes in brain chemicals responsible for communication between nerves. These chemicals include serotonin and endorphins. Although scientists do not understand why these chemical changes take place, they believe the process stimulates pain pathways to the brain and hinders the brain's ability to suppress pain.

Nitric oxide is another chemical linked to tension headaches. It is a substance involved in the transmission of nerve impulses. Researchers believe overproduction of nitric oxide is related to chronic tension headaches. In addition, substances that prevent the production of nitric oxide have been linked to a reduction in the muscle tightness associated with tension headache.